If anyone else called him “little jerk,” Sen. Lindsey Graham might be offended.

But the jab comes from Sen. John McCain, so he wears it like a badge of honor.

“If John’s not belittling you, you’re in trouble,” Graham said. “He calls me lots of other names, too, but they’re not appropriate for the newspaper.”

McCain and Graham aren’t just friends. They’re inseparable, so much so that colleagues, staffers and journalists have begun making cracks about the relationship between the freshman senator from South Carolina and the man who would be president.

Some call Graham a lapdog. Others say he acts as though he’s one of McCain’s legislative aides. One Senate aide, who called Graham and Sen. Joseph I. Lieberman (I-Conn.) “Pips” to McCain’s Gladys Knight, said that Graham “fawns over McCain like there’s no tomorrow.” In the run-up to this week’s hearings for Army Gen. David Petraeus and Ambassador to Iraq Ryan Crocker, The Washington Post’s Tom Ricks said Graham “sometimes seems like McCain’s ‘Mini-Me.’”

“I think it’s almost a father-son relationship,” said Sen. Mel Martinez (R-Fla.), a friend of both senators and another member of their Senate clique. “I think Lindsey looks to [McCain] and relies on him. But I think John draws on Lindsey’s energy and relies on him for a laugh.”

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Tuesday morning was typical. As a curtain raiser for Petraeus’ appearance before the Senate Armed Services Committee, McCain, Graham and Lieberman appeared together outside the Capitol at an event organized by Veterans for Freedom.

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Tuesday was McCain’s first day back at the Capitol in a few weeks. The last time he was there — for votes on the massive budget bill — he and Graham could be seen walking side by side in the Russell building and riding together on the Senate subway. During the late-night vote-o-rama, the two men cracked jokes in the back of the chamber like two grade school pranksters.

“Lindsey! Lindsey! Get over here!” McCain said, his raspy voice wafting up to the gallery, when Graham strayed momentarily and walked in the other direction.

A few days later, when McCain flew home to Arizona for a weekend of relaxation and barbecue, he took Graham with him. Then, together with Lieberman, they traveled on an eight-day journey to Iraq, Jordan, Israel, England and France later in the month.

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It isn’t easy being the nobody-senator next to the somebody-senator-turned-presidential-hopeful. But Graham says he relishes playing the role of McCain’s confidant.

“If I make his day better by being someone he can talk to, confide in, have a good laugh with, I am honored to play that role,” he said. “I enjoy his company.”

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In a sense, the two men owe their friendship to former President Bill Clinton. Graham was a member of the House, serving on the Judiciary Committee, when the panel initiated impeachment proceedings against Clinton. Graham had the task of shipping the impeachment case to the Senate side of Capitol Hill, and that’s when he and McCain met.

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With military issues as their common language, they kept up the communication from opposite ends of Capitol Hill. In 2000, when McCain decided to run for president, he asked Graham for his support.

“He called me out of the blue and said, ‘I’m thinking about running for president. Will you support me?’ Graham recalled. “I said, ‘Sure, yeah, I’ll support you, because you’re the first person who ever asked. What the hell? Why not?’”

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They’ve been through some big fights but perhaps none tougher than the one Graham calls “our campaign,” the current battle for the White House.